The production of very hard surfaces of borides on metal articles by diffusion of boron into the surfaces thereof, has long been known. For this purpose it is possible, for example, to use gaseous boriding agents, such as diborane, boron halides, and organic boron compounds, as well as liquid substances, such as borax melts, with viscosity-reducing additives, with or without the use of electric current. The use of such boriding agents, however, has never gained commercial importance due to the fact that they are not very economical, they are toxic, and because of the non-uniformity of the boride layers obtained therewith. As a result, it remains desirable to provide a metallic object, having at least a portion of a surface of the object that is borided and therefore wear-resistant.